The present invention relates to a mass transfer heat exchanger in which a solution for mass exchange is allowed to flow along the outer walls of heat transmission pipes where it absorbs steam to generate heat, and the heat thus generated is transmitted to a fluid which flows in the heat transmission pipes.
An example of a conventional device of this type is shown in FIG. 1. In FIG. 1, reference numeral 1 designates a tank; 2, heat transmission pipes arranged horizontally in the tank 1; 3, a sprinkling trough for pooling high-density solution 10 used for mass exchange; 4, sprinkling outlets connected to the bottom of the trough 3; 5, a low-density solution lead-out pipe for conveying low-density solution 11 obtained by mass exchange out of the tank 1; 6, a high-density solution lead-in pipe for supplying high-density solution to the sprinkling trough 3; 7, a vapor lead-in pipe for supplying steam 12 into the tank 1; 8, a pump; and 9, a low-density solution discharge pipe.
The device thus constructed operates as follows: A high-density solution 10 is supplied through the high-density lead-in pipe 6 connected to the tank 1 and pooled in the sprinkling trough 3. The solution 10 thus pooled is sprinkled over the heat transmission pipes 2 through the sprinkling outlets 4 at the bottom of the trough 3. While flowing down the outer walls of the heat transmission pipes 2, the high-density solution 10 absorbs vapor 12 supplied through the vapor lead-in pipe 7. As a result, it is changed into a low-density solution while generating heat. The heat thus generated is transmitted to the fluid in the heat transmission pipes 2 through the walls thereof. On the other hand, the solution 11 which has absorbed the vapor 12 is discharged out of the device through the low-density solution lead-out pipe 5 and the low-density solution discharge pipe 9 by the pump 8.
With the conventional mass transfer heat exchanger constructed as described above, if the heat transmission pipes 2 arranged horizontally are long in the axial direction, it is rather difficult to uniformly wet the outer walls of the heat transmission pipes 2 with the high-density solution 10 sprinkled through the sprinkling outlets 4. This tendency is significant especially for the lower heat transmission pipes. In the case where the heat transmission pipes are disposed horizontally, it is necessary to provide a number of sprinkling outlets 4 for the sprinkling trough 3, and accordingly it is difficult to uniformly distribute the high-density solution 10 Further, in the case where the tank 1 is tilted, the high-density solution 10 is not uniformly sprinkled over the outer walls of the heat transmission pipes 2, as is apparent from FIG. 2. Sometimes, the heat exchanger suffers from a difficulty that the amount of high-density solution 10 supplied through the high-density solution lead-in pipe 6 is more than the amount of high-density solution sprinkled through the sprinkling outlets 4, that is, sprinkling the high-density solution is not continuous.
It is clear from the above description that, the conventional mass transfer heat exchanger is disadvantageous in that the heat transmission surfaces are not effectively utilized, and the mass transmission characteristic is poor.